As a developing cartridge mountable in an image forming apparatus employing an electrophotographic method, there is conventionally known a developing cartridge including a developing roller on which toner is carried. The developing cartridge is configured to be mounted in an image forming apparatus in a state where the developing cartridge is mounted in a drum cartridge including a photosensitive drum.
As such a developing cartridge, there is known a developing cartridge including a coupling gear that is configured to receive a drive force from a main body of an image forming apparatus and to transmit the drive force to a developing roller.